Back-Illuminated CMOS Pixel Trench Junction for Dark Current Control
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Solution Overview
Problem
The existing solid-state imaging devices experience deterioration in dark characteristics due to weakened pinning on the silicon substrate, leading to issues like white spots and dark current, particularly when a P-type diffusion layer and an N-type diffusion layer are formed on the sidewall of a trench between pixels.
Innovation Solution
A solid-state imaging device is designed with a PN junction region on the sidewall of a trench between pixels, where the P-type region protrudes below the N-type region, forming a strong electric field to retain electric charge and prevent charge flow into the photodiode, thereby enhancing dark characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a P-type diffusion layer and an N-type diffusion layer are formed on the sidewall of a trench between pixels, then the saturation charge amount Qs of each pixel is increased, but pinning on the light entrance side of the silicon substrate weakens causing dark current and white spots
Solution Approach 1:
The patent segments the diffusion layers into multiple regions with different types and concentrations. Specifically, it forms a first P-type diffusion layer and a second P-type diffusion layer with different impurity concentrations, and similarly divides N-type diffusion layers into multiple regions. This segmentation allows the light entrance side to maintain strong pinning while the light exit side provides sufficient charge storage capacity.
Solution Approach 2:
The patent applies local quality by creating different diffusion layer configurations at different locations. The light entrance side has P-type diffusion layers with higher impurity concentrations to strengthen pinning, while the light exit side has N-type diffusion layers optimized for charge storage. Each region is tailored to its specific functional requirements rather than using a uniform structure throughout.
2Reliability
If the P-type region protrudes below the N-type region in the PN junction region, then a strong electric field is formed to retain electric charge, but the structure complexity increases
Solution Approach 1:
The patent utilizes the depth dimension by making the P-type region protrude below the N-type region in the vertical direction. This three-dimensional configuration creates a strong electric field at the protruding interface, effectively retaining electric charge. The dimensional change from a planar to a protruding structure enables enhanced charge retention without significantly increasing lateral complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents the deterioration of dark characteristics by maintaining strong pinning and reducing dark current and white spots, ensuring improved image quality.
Implementation Method 1
a PN junction region formed on a sidewall of the trench, the PN junction region including a P-type region and an N-type region, in which the P-type region has a protruding region protruding to a lower side of the N-type region
Data Source
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AI summary
The present technology relates to a solid-state imaging device capable of suppressing deterioration in dark characteristics, and an electronic apparatus. The present invention is provided with a photoelectric conversion section that performs photoelectric conversion; a trench that penetrates a semiconductor substrate in a depth direction and that is formed between the photoelectric conversion sections provided in adjacent pixels; and a PN junction region formed on a sidewall of the trench and including a P-type region and an N-type region, the P-type region having a protruding region protruding to the lower side of the N-type region. The present invention is provided with: an inorganic photoelectric conversion section having a pn junction, and an organic photoelectric conversion section having an organic photoelectric conversion film, the inorganic photoelectric conversion section and the organic photoelectric conversion section being stacked in a depth direction from a light-receiving surface side within a same pixel; and a PN junction region formed on a sidewall of the inorganic photoelectric conversion section, the PN junction region including a P-type region and an N-type region. The present invention is provided with: a photoelectric conversion section that performs photoelectric conversion; a trench formed in a semiconductor substrate without penetrating the semiconductor substrate; a PN junction region formed on a sidewall of the trench and including a first P-type region and an N-type region; and a second P-type region formed on a light-receiving surface side of the photoelectric conversion section. The present technology can be applied to, for example, a back-illuminated CMOS image sensor.